Acetylenically and ethylenically unsaturated ketones may be used as a starting material for the preparation of jasmone-type compounds and of polymers. The synthesis of one of such ketones, 1-pentene-3-one-4-yne, is described in Tetrahedron 33 (1977) 2813-2817, but this synthesis is very complicated. It has now been found that such ketones can be prepared with high selectivity and in an acceptable yield using relatively simple starting compounds.